Experimental studies of immobilized-yeast,packed-bed reactors with reduced CO2 entrapment

A horizontal packed-bed reactor with baffles (HPBR) and a continuously stirred tank reactor with intermittent paddle agitation have been shown to considerably reduce the CO₂ entrapment when glucose is fermented with immobilized baker’s yeast in calcium alginate beads. Using high cell contents in the gel resulted in internal mass transfer hindrance. The highest productivity was obtained with the HPBR giving 29 g EtOH/Lh at an ethanol yield of 90%. The substrate used was 100 g/L glucose. Fermentation of lactose and deproteinized whey by coimmobilized baker’s yeast and |3-galactosidase resulted in much lower productivity-about 5 g EtOH/L.h because of the slow fermentation of galactose.     

Standard potential of the silver-silver chloride electrode in 10, 20, and 40 wt.% ethanol/water solvents at 25, 0, −5, and −10°C

In order to facilitate the measurement of thermodynamic quantities at temperatures below 0°C in ethanol/water solvents, the standard potential of the silver-silver chloride electrode in 10, 20, and 40 wt.% ethanol has been determined at 25, 0, ?5, and ?10°C. Electromotive force measurements of cells of the type $$Pt;H_2 (g)|HCl(m) in EtOH/H_2 O|AgCl;Ag$$ were used. The potentials found at 25°C were in good agreement with earlier results. Mean activity coefficients for hydrochloric acid in the three mixed solvents were derived.     

Facile formation of stimuli-responsive,fluorescent and magnetic nanoparticles based on cellulose stearoyl ester via nanoprecipitation

In comparison to stimuli-responsive, multi-functional nanoparticles (NPs) from synthetic polymers, such NPs based on sustainable, naturally occurring polysaccharides are still scarce. In the present study, stable stimuli-responsive, fluorescent and magnetic NPs were fabricated using cellulose stearoyl esters (CSEs) consisting of cellulose and stearoyl groups. The multifunctional NPs with the average diameters between 80 and 250 nm were obtained after facile nanoprecipitation using CSE solutions containing Fe₃O₄-NPs. Using the aqueous solution of fluorescent rhodamine B as precipitant, NPs with rhodamine B on NP surface were obtained. Rhodamine B could be released depending on the temperature. In comparison, stearoylaminoethyl rhodamine B can be encapsulated in CSE-NPs, which renders obtained NPs reversible fluorescence in response to UV illumination and heat treatment.     

New rare-earth metal acyl pyrazolonates: Synthesis,crystals structures,and luminescence properties

Ligand 3-methyl-1-phenyl-4-stearoylpyrazol-5-one (HQ) is synthesized and used to obtain new complexes of rare-earth metals (Eu, Gd, and Tb) of the composition [Ln(Q)₃(H₂O)(EtOH)]. The crystal structure of the terbium complex is determined by X-ray diffraction analysis (CIF file CCDC 975286). In a molecule of the complex, three aliphatic fragments n-C₁₇H₃₅ are codirected, which results in the formation of layers bound according to the fastener-sticker principle. The molecules of the complex are joined by a hydrogen bond network involving the pyrazolone rings and oxygen atoms of the inner-sphere solvent molecules (H₂O and EtOH). The terbium complex is luminescent at room temperature, whereas the luminescence of the europium complex is very weak at room temperature and increases by 60 times at lowered temperatures. This makes it possible to consider these compounds as a new class of “luminescent thermometers.”     

Kinetics and possible mechanism of hydrogen chloride oxidation over supported copper-containing salt catalysts: II. Kinetics of HCl oxidation in the deacon and methane oxychlorination reactions over the CuCl2-KCl-LaCl3 catalyst

The kinetics of HCl oxidation at 350–425°C over the supported CuCl₂-KCl-LaCl₃ catalyst has been investigated using a gradientless technique. The HCl oxidation kinetics in the Deacon and methane oxychlorination reactions has been studied in order to substantially extend the \(Cl_2 \left( {P_{Cl_2 } } \right)\) partial pressure variation range. When the reaction rate is independent of P _HCl, HCl oxidation on the copper-potassium catalysts is described by the same rate equation, irrespective of whether the catalyst contains lanthanum or not. The introduction of lanthanum chloride increases the HCl oxidation rate by one order of magnitude. The rate equation obtained has significant advantages over the equation corresponding to the Kenney-Slama equation. The kinetic features of HCl oxidation over the lanthanum-containing catalyst, whether the process depends on P _HCl or not, can be explained in terms of the superposition of the Kenney-Slama dissociative mechanism and the catalytic mechanism suggested here. The role of lanthanum chloride in both HCl oxidation pathways is considered.     

Impact of PS/SiO2 morphologies on the SERS activity of PS/SiO2/Ag nanocomposite particles

To understand the relationship between the morphology of carboxyl-functionalized polystyrene/silica (PS/SiO₂) nanocomposite microspheres and the surface-enhanced Raman scattering (SERS) performance of PS/SiO₂/Ag nanocomposite particles, core-shell and raspberry-like PS/SiO₂ composite microspheres were used as templates to prepare PS/SiO₂/Ag nanocomposite particles. The core-shell and raspberry-like structured PS/SiO₂ templates were prepared via in situ sol-gel reaction by hydrolysis tetraethyl orthosilicate (TEOS) in alkali solution. Silver nanoparticles (10–50 nm) were loaded on the PS/SiO₂ templates’ surface by chemical reduction. The morphology and structure of the PS/SiO₂/Ag particles were characterized by TEM, SEM, X-ray diffraction (XRD), and ultraviolet-visible (UV-vis) spectroscopy. Rhodamine 6G (R6G) was selected as a model chemical to study the enhancement performance of substrate constructed by PS/SiO₂/Ag nanocomposite. Results indicated that the PS/SiO₂/Ag nanocomposite prepared based on the core-shell templates showed higher SERS activity. The beneficial effect was associated with a lower specific area of core-shell structure and the larger average diameter of nanosilvers than that of the raspberry-like templates.     

Synthesis and spectroscopic characterization of Zn(II), Cd(II), and Hg(II) ciprofloxacin complexes

Ciprofloxacin metal co mplexes with general for mula [M(CPF)₂]X₂·nH₂O [M = Zn(II), Cd(II), and Hg(II)] have been synthesised and characterized using elemental analysis (CHN), spectroscopic (UV-Vis, IR, MS, and ¹H NMR) and ther mogravimetric (TG and DTA) data. Using the Coats-Redfern and Horowitz-Metzeger methods, kinetic analysis of the thermogravimetric data had been performed.     

Synthesis,structures, sorption and magnetic properties of coordination polymers based on 3d metal pivalates and polydentate pyridine-type ligands

The reactions of 3d metal pivalates with pyridine-containing ligands of different structures afforded the 1D coordination polymers [Co₂(Piv)₄(dpe)₂] _n , [Ni(Piv)₂(dpe)(EtOH)₂] _n , [Cu₂(Piv)₄(dpe)] _n , [Cu(Piv)₂(dpe)] _n , [Ni(Piv)₂(4-ptz)(EtOH)₂] _n , and [Cu₂(Piv)₄(4-ptz)· ·mSolv] _n (Solv is EtOH, m = 2; Solv is C₆H₆, m = 1; Piv^? is pivalate, dpe is trans-1,2-bis(4-pyridyl)ethylene, 4-ptz is 2,4,6-tris(4-pyridyl)-1,3,5-triazine), as well as the 3D coordination polymer [{Cu₂(Piv)₄}₃(3-ptz)₂] _n (3-ptz is 2,4,6-tris(3-pyridyl)-1,3,5-triazine). The sorption and magnetic properties of a series of the synthesized compounds and magnetic properties of the earlier characterized coordination polymer [Mn₂(O₂CC₆H₅)₄(dpe)₂·dpe] _n were studied. It was shown that the desolvation of the complexes [Ni(Piv)₂(4-ptz)(EtOH)₂] _n and [Cu₂(Piv)₄-(4-ptz)·2EtOH] _n resulted in the formation of the crystal structures, in which the pores are accessible to nitrogen and hydrogen at 78 K (S _BET are up to 92 m² g^?1). The temperature dependences of the molar magnetic susceptibility for [Co₂(Piv)₄(dpe)₂] _n , [Mn₂(O₂CC₆H₅)₄-(dpe)₂·dpe] _n , [Ni(Piv)₂(dpe)(EtOH)₂] _n , [Ni(Piv)₂(4-ptz)(EtOH)₂] _n , and [Cu₂(Piv)₄-(4-ptz)·2EtOH] _n are described in terms of models taking into account the zero-field splitting and exchange interactions or isotropic exchange Hamiltonians.     

On the determination of HCl+ (A,v′) vibrational populations from HCl+ (A→X) fluorescence spectra: direct comparison between photoionization and penning ionization

Using a beam apparatus, we have measured the HCl⁺ (A,v′→X,v″) fluorescence spectra of HCl⁺ (A,v′) ions formed in HeI (58.4 nm), and NeI (73.6 nm) photoionization and, for the first time, in He (2³ S) Penning ionization under single collision conditions with a wavelength bandwidth around 1 nm. In addition, we have studied Ne (3s ³ P _{2, 0}) Penning ionization of HCl at three different collision energies. The procedure and the problems in extracting HCl⁺ (A,v′) vibrational populations from the data are discussed in some detail. Thedirect comparison of photoionization and Penning ionization data allows definitive conclusions to be drawn on the question whether final state interactions in the Penning reaction change the “nascent” vibrational population (determined by electron spectrometry); for He (2³ S)+HCl, such changes are shown to be absent within the experimental uncertainty (<±10%). For Ne (3s ³ P _{2, 0})+HCl, the HCl⁺ (A,v′=0, 1) populations are also found to be close to those measured by electron spectrometry and essentially independent of collision energy in the range 34–96 meV. From measurements of the fluorescence intensity as a function of HCl density, we have evidence for a fast loss of HCl⁺ (A,v′) ions in collisions with HCl (rate constant around 5·10^?9 cm³s^?1).     

A photoionization study of the van der Waals molecule C2H4 · HCl

The dissociation energy of the C₂H₄ · HCl van der Waals complex was determined to be 3.18±0.73 kcal mol^?1 by a dissociative photoionization technique. C₂H₄ · HCl was produced by free expansion of a 1:4 mixture of C₂H₄ in HCl and the clusters were ionized with tunable synchrotron radiation. The photoionization efficiency function of (C₂H₄ · HCl)⁺ from C₂H₄ · HCl was determined between 600 and 1,300 Å and the onset for (C₂H₄ · HCl)⁺ was established as 1,163±2 Å = 10.66±0.02 eV; these values give ΔH _f ⁰ (C₂H₄ · HCl) = ?10.7±0.7 kcal mol^?1 and ΔH _f ⁰ (C₂H₄·HCl⁺)=235.1±0.9 kcal mol^?1. A complex ion dissociation energyD ₀(C₂H₄ · HCl⁺) = ?0.3±0.9 kcal mol^?1 was calculated from the results. The major features on the PIE curve for C₂H₄ · HCl⁺ can be analyzed in terms of the known energetic features of C₂H ₄ ⁺ and HCl. An extended energy diagram for the C₂H₄ + HCl system is presented.     

Effect of Cl substituent in the aromatic tetracycline ring on its reactivity with solvated electrons

Decomposition yields of tetracycline hydrochloride /TC.HCl/ and chlorotetracycline hydrochloride /ClTC?HCl/ in methanol solution saturated with Ar or N₂O were determined. Rate constants of the reaction e_s with some antibiotics were obtained: $$\begin{gathered} k/e_s^ - + ClTC \cdot HCl/ = 2 \cdot 49 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} ; \hfill \\ k/e_s^ - + TC \cdot HCl/ = 2 \cdot 86 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} \cdot \hfill \\ \end{gathered} $$ On the basis of the diffence between decomposition yields: ΔG=G_?TC.HCl^?G?ClTC.HCl′ 7-C?Cl group decomposition yield and the rate constant $$k/e_s^ - + Cl - C - 7/ = 7 \cdot 94 \times 10^8 dm^3 \cdot mole^{ - 1} \cdot s^{ - 1} $$ were determined. It was demonstrated by¹H NMR that the radical formed by degradation of 7-C?Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride /TC.HCl/.     

Polyoxotungstate nanoclusters supported on silica as an efficient solid-phase microextraction fiber of polycyclic aromatic hydrocarbons

A highly porous silica-supported tungstophosphoric acid (PW) nanocluster was prepared for use in solid-phase microextraction (SPME) of polycyclic aromatic hydrocarbons (PAHs). The PWs represent a class of discrete transition metal-oxide nanoclusters and their structures resemble discrete fragments of metal-oxide structures of definite size and shape. Transition metal-oxide nanoclusters display large structural diversity, and their monodisperse sizes can be tuned from several Ångstroms up to 10 nm. The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The nanomaterial was immobilized on a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS. Analytical merits include limits of detection that range from 0.02 to 0.1 pg mL^?1 and a dynamic range as wide as from 0.001 to 100 ng mL^?1. Under optimum conditions, the repeatability for one fiber (n?=?3), expressed as the relative standard deviation, is between 4.3 % and 8.6 %. The method is simple, rapid, and inexpensive. The thermal stability of the fiber and the high relative recovery make this method superior to conventional methods of extraction.

The highly porous silica-supported tungstophosphoric acid nanocluster material is found to be capable of efficiently extracting PAHs from aqueous sample solutions. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. Following thermal desorption, the PAHs were quantified by GC-MS.     

Thermal decomposition of polymethylmethacrylate synthesized with anionic catalysts

TG and DTA data are used to show that the thermal decomposition of polymethylmethacrylate (PMMA) synthesized with anionic catalysts depends on the nature of the catalyst. It is found that the thermal stability of PMMA obtained by using anionic amide catalysts is higher than that of radical PMMA and of PMMA obtained with other anionic catalysts, and depends on the temperature of polymerization and on the molecular weight of the polymer.     

Mechanism and improvement of complex formation between LPS and polymyxin B that is immobilized on an ion exchanger

Polymyxin B was immobilized on the ion exchanger, Amberlite IRC-50. The modified support was used as an adsorbent for lipopolysaccharide ofE. coli from a phosphate buffer at pH = 7.0 and T = 20°C. The insertion of a spacer, 6-amino hexanoic acid, improved the adsorption capacity of the modified carrier significantly. Upon partial acetylation (25%) of primary amino groups of immobilized Polymyxin B, the adsorption capacity of the support was halved. From our results, it is concluded that the complex formation between lipopolysaccharide and immobilized Polymyxin B is based on both lipophilic, as well as electrostatic, interactions. Convenient procedures for the immobilization of the ligands and the characterization of the ion exchanger are described.     

Visual detection of arginine,histidine and lysine using quercetin-functionalized gold nanoparticles

We report on the use of quercetin-functionalized gold nanoparticles (QC-AuNPs) as a colorimetric probe for the amino acids arginine (Arg), histidine (His) and lysine (Lys). The method is based on the aggregation of the QC-AuNPs that is caused by these amino acids and leads to a visually detectable color change from red to blue. The absorption maxima shift from 525 nm to 702, 693, and 745 nm, respectively. Aggregations are confirmed by dynamic light scattering (DLS) and transmission electron microscopic techniques (TEM). The effects of the QC concentration, temperature and reaction time for the preparation of QC-Au NPs were tested. Other amino acids do not interfere. Under the optimal conditions, linear relationships exist between the absorption ratios at 702/525 nm (for Arg), 693/525 nm (for His), and 745/525 nm (for Lys) over the concentrations ranges from 2.5–1,250 μM (Arg) and 1–1,000 μM (His and Lys), respectively. The respective limits of detection are 0.04, 0.03, and 0.02 μM. The method provides a useful tool for the rapid visual and instrumental determination of the three amino acids. Figure

We report the use of quercetin as novel reagent for preparation and functionalization of gold nanoparticles to colorimetric sensing of three aminoacids (arginine, histidine and lysine). This is based on the aggregation of QC-AuNPs induced by three aminoacids.     

Activity coefficients for NaCl in ethanol-water mixtures at 25°C

Activity coefficient values for NaCl in ethanol-water mixtures containing 20, 40, 60, 70, 80 and 90 weight % ethanol are calculated from the emf for the galvanic cell $$Na - glass|NaCl(m), H_2 O (100 - Y), EtOH(Y), AgCl|Ag$$ in which the weight % of the corresponding solvent is indicated in parenthesis. The results obtained are analyzed by using different theoretical models. Chemical models which take into account the presence of ion pairs in solutions of high ethanol content are also used. There is good agreement between the results obtained from all the models.     

Largely enhanced molecular orientation and mechanical property of injection-molded high-density polyethylene parts via the synergistic effect of polyamide 6 in situ microfibrillar and intense shear flow

The high-density polyethylene (HDPE)/polyamide 6 (PA6) in situ microfibrillar composites (HAM-C) were fabricated by the “extrusion-hot stretch-quenching” technique, in which PA6 microfibrillar had diameters lying in the range 0.55 to 1.05 μm. Then the HAM-C and pure HDPE were processed by multi-melt multi-injection molding (MMMIM). The effect of PA6 in situ microfibrillar and secondary melt penetration on the crystalline morphologies and mechanical properties was investigated using a variety of characterization techniques including differential scanning calorimetry (DSC), rheological experiments, scanning electron microscopy (SEM), synchrotron two-dimensional small-angle X-ray scattering (SAXS), and tensile testing. It was found that PA6 microfibrillar not only acted as a heterogeneous nucleation agent, but also prolonged the relaxation time of HDPE matrix by suppressing the mobility of HDPE molecular chains. It was revealed, from observing the morphologies, that the presence of PA6 microfibrillar not only facilitated the formation of transcrystalline superstructures on its surface, but also induced much more oriented crystals nearby as a result of the amplified local shear field. Furthermore, SAXS results confirmed that the degree of orientation of the injection-molded HAM-C part (HAM-M) was largely enhanced. Finally, the tensile testing showed that the tensile strength and Young’s modulus of the HAM-M sample were enhanced by 38.8 and 54.6 %, respectively, when compared with pure HDPE parts. This work provides a promising way to tailor the crystalline structure of the injection-molded parts.     

TiO2 and TiO2/SiO2 nanoparticles obtained by sol–gel method and applied on dye sensitized solar cells

In this work we show the synthesis and characterization of TiO₂ and TiO₂/SiO₂ nanoparticles synthesized by sol–gel method using HF and HCl as catalysts. The obtained nanoparticles were analyzed by N₂ adsorption–desorption isotherms, transmission electronic microscopy, Ultraviolet–visible spectroscopy and X-ray diffractometry. Mesoporous, homogeneously polycondensed TiO₂/SiO₂ materials, containing nanocrystalline anatase phase with band gap similar to pure titania were obtained. Films of the powdered oxides were applied to assemble dye sensitized solar cells that presented electrical parameters, Fill Factor and efficiencies similar to devices obtained by only TiO₂. The sol–gel route arises as an alternative way to prepare TiO₂/SiO₂ materials for solar cells.     

Organelle sensor: amperometric determination of nadh by immobilized mitochondrial electron transport particles

A new sensor for NADH was developed by making use of an immobilized subcellular organelle. Mitochondria was used as a model system for assembling an organelle sensor. Mitochondrial electron transport particles (ETP) were prepared from beef heart muscle and entrapped in the membrane formed of agar gel. The membrane-bound ETP was found capable of NADH oxidation: $$NADH + \tfrac{1}{2}O_2 + H^ + \xrightarrow{{ETP}}NAD^ - + H_2 O$$ The membrane was tightly attached to the surface of an oxygen electrode capable of amperometric detection of O2. The sensor responded to NADH in solution with a resulting electric output. The response was enhanced by the addition of 2,4-dinitrophenol (DNP). NADH was determined in the concentration range 1–300 µM. NADH was alternatively determined for 2 weeks without replacing the ETP-bound membrane.     

Extraction and chemical investigation of jute (Corchorus olitorius,Linn.) seed protein

Studies were made on the protein solubility of deoiled jute (Corchorus olitorius, Linn.) seed in aqueous solution over various pHs and in different concentrations of NaCl at pH 8.0. Chemical analysis of the seed protein showed 16 amino acids, of which 9 were essential. Gel filtration on Sephadex G-200 revealed the presence of four components, and their molecular weights were determined by two standard methods. Extractable jute seed proteins in salt solution were separated into six fractions electrophoretically (SDS-PAGE). The molecular weights of the six fractions were found to be 118,000; 103,000; 96,000; 67,500; 48,500; and 15,000.